The lipids of gastric mucosa and of the cell membranes contained therein are undoubtedly important structural and functional components. Yet very little is known of the mechanism and controls for their biosynthesis and degradation. We have shown that dipalmitoyl phosphatidylcholine constitutes 31% of the rat gastric phosphatidylcholine. The only other tissue having such a high concentration of this constituent is lung tissue and surfactant. We propose to elucidate the mechanism of synthesis of dipalmitoyl phosphatidylcholine using everted gastric mucosa and also suspensions of surface mucosal cells, parietal cells and organelles. These preparations will be incubated in media containing appropriately labeled precursors and at various times the products of reaction will be analyzed. Prelabeled mucosa and cell suspensions also will be incubated with unlabeled medium to study degradation of phospholipids. In a separate approach, rats will be fed various diets to determine whether gastric phospholipids and other lipids (including cholesterol) are readily modified by diet. Functional aspects of such changes will be investigated.